The present invention relates generally to systems and methods for sperm sorting.
According to estimates, there are more than 70 million infertile couples worldwide. Approximately 1 in every 4 infertile couples seek clinical treatment, where, according to sources, male factor may account for about 50 percent of the infertility cases. Assisted reproductive technology (ARTs), such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and intrauterine insemination (IUD, are generally utilized in reproductive clinics to treat infertile couples. With an increasing rate of male infertility due to environmental and physiological conditions, there is an ever growing need for the use of ARTs in reproductive clinics. Isolation of the most motile and morphologically normal sperm is an integral process to commonly used IVF/ICSI procedures. Selection of healthy sperm from unprocessed semen (stock sperm) is crucial as it requires selecting sperm that is not only highly motile, but also has a normal morphology, mature nuclei, and lesser reactive oxygen species (ROS) production. Although current IVF/ICSI procedures results in successful pregnancy approximately 50 percent of the time, the output can be greatly compromised if the sperm being selected are abnormal.
Currently, the more commonly-known ART techniques use centrifugation based sperm swim-up, density gradient separation methods, and microfluidic based methods with/without the use of chemotaxis to sort sperm. These techniques have potential drawbacks and limitations in their use for procedures as delicate as IVF/ICSI. It is worth noting that the centrifugation based sperm sorting techniques, such as swim-up, compromise on sperm quality during the repetitive centrifugation steps. Quality of a sperm sample is degraded during swim-up technique due to ROS generation. ROS exposure can greatly harm the DNA of seemingly motile and healthy sperm. Furthermore, the centrifugation-based sperm sorting techniques are labor intensive, and outcome can vary from technician to technician.
Sperm sorting technologies based on microfluidics have an advantage because they can precisely handle small volume of sperm samples. On the other hand, microfluidic-based sperm sorting devices have very low throughput and can only process small semen volumes, such as 2 μl-50 μl, which limits their application to reproductive clinics, where normal sperm sample can have volume of 1.5 ml.
In a clinical ICSI procedure, an embryologist will have on average 20 oocytes that can be handled in four petri dishes, and will need 20 sperm. The embryologist would like to choose these 20 sperm in an oligospermic sample among a few hundred sperm. Such scenario would require real-time monitoring of individual sperm and collection from outlet when 20 sperm reach the outlet, which is not attainable using current clinical or microfluidic technologies. In a second procedure, where an embryologist is handling healthy samples, in vitro fertilization is performed using 0.5 million healthy sperm suspended in a 5-20 μl suspension to be introduced to an oocyte. However, current sorting systems, such as described above, do not provide the throughput needed to meet these criteria.
Traditionally, optical microscopes have been used to image sperm for computer assisted sperm analysis (CASA) and manual identification of sperm motility for ARTs. This classical approach has limitations in tracking a large number of sperm simultaneously due to its small field of view (FOV). In addition, sperm tracking and motility analyses are performed after sorting. Currently no system exists that can sort and analyze sperm simultaneously.
It would therefore be desirable to provide a system and method for processing, including as sorting, sperm without damaging the sperm or subjecting the sperm to potentially-damaging conditions. Furthermore, it would be desirable to provide a system and method that can analyze sperm, but is efficient and able to scale.